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ANSC 315 > Module 3- Carbohydrate metabolism > Flashcards

Module 3- Carbohydrate metabolism Flashcards

1
Q

major source of energy in the diet

A

carbs

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2
Q

carbs make up (%) of caloric intake in monogastrics & ruminants

A

50

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3
Q

what is the most important carb in plants

A

starch

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4
Q

T or F: lignin is a carb

A

F

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5
Q

3 roles of carbs in plants

A

1) tissue synthesis
2) energy reserve
3) structural support

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6
Q

T or F: very little storage of carbs in animals

A

T

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7
Q

what 3 body compartments hold the little bit of stored carbs

A

bloodstream, liver & muscle

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8
Q

carbs can make up to what % in animals diets

A

70%

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9
Q

T or F: less than 1% of carbs are stored in the body

A

T

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10
Q

how are carbs classified

A

based on number of sugar units

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11
Q

lactose

A

glucose + galactose

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12
Q

sucrose

A

glucose + fructose

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13
Q

maltose

A

glucose + glucose

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14
Q

what are the 2 most important carb groups from a nutritional & functional standpoint

A

1) pentose
2) hexoses -> glucose

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15
Q

what configuration of glucose is recognized by the digestive enzymes in the GI tract

A

D

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16
Q

T or F: animals cannot utilize L forms of glucose

A

T

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17
Q

3 most important hexoses

A

1) glucose
2) galactose
3) fructose

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18
Q

2 major end products of fermentative digestion

A

1) VFA in rumen
2) glucose in small intestine

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19
Q

2 most important pentose sugars. why?

A

ribose + deoxyribose
- need for DNA/RNA synthesis

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20
Q

adenosine =

A

ribose & adenine

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21
Q

major function of ribose

A

structural component of NAD & NADH

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22
Q

NADH is the ( ) form

A

reduced

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23
Q

riboflavin is a component of ( ) and ( )

A

FAD & FMN -> co factors in electron transfer REDOX reactions

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24
Q

T or F: ribose can covert tryptophan into niacin

A

T

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25
Q

glycosidic linkage

A

OH group on anomeric C

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26
Q

anomeric carbon

A

carbon double bonded with O2

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27
Q

alpha vs beta glucose

A

alpha: OH group is on amomeric carbon OPPOSITE side of ring structure
beta: OH group on anomeric carbon is on SAME side of ring structure

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28
Q

what dictates if glycosidic linkage is alpha or beta

A

orientation of OH group on carbon #1

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29
Q

monogastrics can only digest ( ) linkages

A

alpha

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30
Q

lactose has ( ) linkage

A

beta

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31
Q

maltose has ( ) linkage

A

alpha

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32
Q

partial digestion yields ( ) in small intestine

A

maltose

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33
Q

( ) is an intermediate in digestion

A

maltose

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34
Q

3 examples of polysacharides

A

starch, cellulose & glycogen

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35
Q

2 classes of polysaccharides + examples

A

1) homo: made of same monosaccharide units (cellulose)
2) hetero: made of diff monosaccharide units (hemicellulose)

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36
Q

2 types of starch granules

A

1) amylose
2) amylopectin

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37
Q

how do amylose & amylopectin differ?

A

structure

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38
Q

high amylose = ( ) amylopectin

A

low

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39
Q

amylose is ( ) digested

A

slowly
- pulses: peas & lentils

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40
Q

amylopectin is ( ) digested

A

rapidly, cereal crops

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41
Q

what happens to amylose structure as it is dissolved in water?

A

the straight unbranched chain turns into a helical structure to reduce surface area for digestive enzymes to digest polysaccharide chains

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42
Q

resistant starch is ( ) in amylose content

A

higher

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43
Q

amylose structure

A

long unbranched chains of glucose
- a (1,4) linkage

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44
Q

amylopectin structure

A

branched chain polymer with a (1,4) and a (1,6) linkages

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45
Q

why is amylopectin digested at a faster rate?

A

branches = more surface area for enzymes

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46
Q

what is the storage form of glucose in animals

A

glycogen

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47
Q

T or F: plants have glycogen

A

F

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48
Q

difference between glycogen storage in liver vs skeletal muscle

A

liver: glycogen is not used locally
skeletal muscle: glucose is used locally (does not go to other tissues)

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49
Q

cellulose

A

long linear polymer of repeating glucose
- b (1,4) linkage

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50
Q

difference between cellulose & starch

A

cellulose: b (1,4) linkage
starch: a (1,4) linkage

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51
Q

hemicellulose

A

heterogenous group of polysaccharide substances
- b (1,4) linkages

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52
Q

poly-phenolic compound example

A

lignin

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53
Q

lignin content ( ) as plant matures

A

increases

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54
Q

hemicellulose has ( ) backbones & side chains

A

sugar

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55
Q

pectin is not digestible by mammalian enzymes but it is susceptible to

A

microbial fermentation

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56
Q

b-glucans linkages

A

b (1,3) + b (1,4)

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57
Q

T or F: cellulose is insoluble in water

A

T

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58
Q

T or F: b-glucans are water soluble

A

T

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59
Q

example of soluble fiber

A

b-glucans

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60
Q

soluble fiber

A

forms a viscous material in GI tract which reduces penetration of digestive enzymes and reduces digestion

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61
Q

what 2 feeds are high in b-glucans

A

barley & oats
- must add beta-glucanase to reduce visocity
- only done in monogastric & poultry diets

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62
Q

soluble xylans

A

form viscous environment that reduces nutrient digestibility

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63
Q

xylanase

A

breaks down xylans

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64
Q

2 major sources of xylans

A

barley & wheat

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65
Q

dietary fiber

A

component of xylan foods that you are eating
-intrinisic component

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66
Q

functional fiber

A

supplement added into diet
- components: pectins & xylans

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67
Q

2 components of functional fiber

A

pectins & xylans

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68
Q

why is high viscosity of fibre beneficial in human diets?

A

1) slows gastric emptying = feel full faster
2) reduces absorption of fat

69
Q

2 properties of soluble fiber

A

1) solubility
2) water holding capacity

70
Q

2 properties of insoluble fiber

A

1) absorption & binding ability
2) degradability/fermentability

71
Q

T or F: insoluble fibers act as pre-biotics

A

T

72
Q

what type of carbs are the only ones that can be absorbed in monogastric GI tract

A

monosaccharides

73
Q

mammalian enzymes can only breakdown what linkages

A

a (1,4) or a (1,6)

74
Q

why doesn’t any carb digestion happen in the stomach of monogastrics?

A

too acidic for salivary amylose to be active

75
Q

T or F: a (1,6) linkage is not susceptible to salivary amylase but a (1,4) is

A

T

76
Q

major enzyme that initiates carb digestion in the mouth in monogastrics

A

salivary amylase

77
Q

where can a (1,6) linkages be broken down in monogastrics

A

small intestine

78
Q

how are dextrins formed

A

formed from initial digestion of starch in the mouth

79
Q

limitation to carb digestion in mouths of monogastrics

A

short amount of time food stays in the mouth

80
Q

what is flowing out of the mouth -> stomach during monogastric carb digestion

A

dextrins & starch (amylose & amylopectin)

81
Q

stomach pH of monogastrics

A

1-2

82
Q

issue with carb digestion in the stomach

A

too acidic

83
Q

where is pancreatic juice secreted into during monogastric carb digestion

A

duodenum

84
Q

T or F: pancreatic amylase cannot digest a (1,6) linkages

A

T

85
Q

limit dextrins vs dextrins

A

limit dextrins are smaller but still have branch points

86
Q

maltase

A

digests maltose to produce 2 glucose units

87
Q

what is the only enzyme that can digest a (1,6) linkages? where is it located?

A

alpha-dextrinase
- brush border enzyme -> located on villi/microvilli

88
Q

lactase

A

breaks down lactose to produce glucose & galactose

89
Q

difference between lactose & sucrose

A

lactose has b (1,4) linkages

90
Q

absorption of monosaccharides in monogastrics uses what 2 types of transport?

A

active & facilitated transport

91
Q

basolateral membrane

A

where blood is flowing, nutrients are absorbed here

92
Q

glucose is ( ) in concentration that galactose in monogastrics

A

higher

93
Q

SLGT-1

A

receptor that is expressed in villi & microvilli
- function depends on presence of sodium

94
Q

SLGT-1 uses GLUT ( ) to transport glucose from ( ) to ()

A

2, enterocyte, bloodstream

95
Q

Na/K ATPase pump

A

pumps 3 Na out & 2 K in

96
Q

what % of energy is dedicated to the Na/K ATPase pump

A

40-50%

97
Q

how does glucose facilitated transport work

A

glucose concentration on luminal side is higher than in cell = move from high to low concentration (aka into bloodstream)

98
Q

how is fructose transported into the cell?

A

uses GLUT 5 transporter to be facilitated inside cell then GLUT 2 to move to bloodstream

99
Q

hydrolysis of ATP

A

ATP -> ADP

100
Q

glucose is metabolized by the ( ) and released into ( ) to be used by other tissues

A

liver, peripheral circulation

101
Q

how do galactose & fructose provide energy?

A

they get converted into glucose derivates via phosphorylation reactions so they can now enter glucose metabolic pathways

102
Q

what 2 GLUT are most important for transporting glucose from bloodstream -> into cell

A

GLUT 2 & GLUT 4

103
Q

where is SLGT-1 expressed?

A

only the small intestine

104
Q

what GLUT is insulin dependent

A

GLUT 4

105
Q

insulin is released in response to

A

glucose

106
Q

what GLUT are insulin independent?

A

all but GLUT 4

107
Q

GLUT 1

A

basic supply of glucose to cells

108
Q

GLUT 2

A

low infinity transporter
glucose -> blood

109
Q

GLUT 3

A

high affinity transporter for brain & other glucose dependent tissues

110
Q

GLUT 4

A

insulin sensitive
muscle & tissues

111
Q

GLUT 5

A

fructose

112
Q

1 mol of glucose when completely oxidized yields ( ) mols of ATP

A

38

113
Q

2 glucose fates

A

1) complete oxidation via glycolysis
2) fatty acid synthesis/energy storage

114
Q

what kind of relationship is present between the rumen & its microorganisms

A

symbiotic

115
Q

by-product of pre-gastric carb fermentation in ruminants

A

VFAs

116
Q

structural carbs

A

mostly grazed, fermentative digestion allows nutrients to get energy from these

117
Q

glucose metabolism to VFA yields ( ) mols of ATP

A

2-4

118
Q

anaerobic vs aerobic conditions: ATP yields

A

anaerobic: 1 mol of glucose = 2-4 mols ATP
aerobic: 1 mol glucose = 38 mols ATP

119
Q

what is produced when acetate & butyrate are produced

A

H ions

120
Q

methane loss is associated with a significant energy loss of ( )

A

H

121
Q

the more acetate & butyrate produced = more ( ) produced in rumen

A

methane

122
Q

T or F: propionate does not produce H ions

A

T

123
Q

why is it favourable to have more propionate in the rumen compared to acetate & butyrate?

A

less energy is wasted as methane

124
Q

energy for ruminants comes from

A

fermentation

125
Q

cellulolytic microorganisms

A

ferment fiber -> cellulose, hemicellulose, pectin
- produce acetate (acetate like fermentation)
- neutral pH bc more fiber = more chewing

126
Q

amylolytic microorganisms

A

ferment starch
- produce propionate (propionate like fermentation)
- more acidic rumen

127
Q

T or F: butyrate will always stay at same proportion but acetate & propionate will change

A

T

128
Q

starch is ( ) fermentable than fiber which means more ( ) are produced

A

more, VFAs

129
Q

90% of VFAs are absorbed in the

A

rumen

130
Q

higher feed intake = more ( ) and less ( )

A

propionate, acetate

131
Q

lower frequency of feeding = more ( ), less ( )

A

propionate, acetate

132
Q

4 ways to increase acetate production in the rumen

A

1) feed more frequently
2) increase dietary forage
3) larger particle size
4) buffers

133
Q

rumensin function

A

increase propionate production = decrease methane = increase feed efficiency
- prouce acetate type fermentation

134
Q

gram ( ) bacteria decrease with rumensin

A

positive

135
Q

how does rumensin prevent acidosis

A

decreases lactate

136
Q

T or F: rumensin does not change stomach pH

A

T

137
Q

how are VFAs absorbed?

A

across rumen wall into blood stream via passive & facilitated diffusion

138
Q

once absorbed, acetate & butyrate are metabolized into ( )

A

ketone bodies

139
Q

what ketone bodies are acetate & butyrate metabolized into?

A

B-hydroxybutyrate & acetoacetate

140
Q

t or F: propionate is not metabolized in rumen epithelium during absorption

A

T

141
Q

major function of propionate

A

produce glucose via gluconeogenesis

142
Q

post-absorptive metabolism of VFAs (how do they each enter TCA cycle?)

A

acetate & butyrate: enter TCA cycle as acetyl CoA
propionate: enter TCA cycle as succinyl CoA

143
Q

what is the only VFA that can produce glucose?

A

propionate

144
Q

why would no propionate be shown in a blood sample?

A

bc all of it is extracted by the liver

145
Q

what VFA is absorbed in the largest amounts

A

acetate

146
Q

what is the major circulating energy substrate in ruminants vs monogastrics

A

r- acetate
m- glucose

147
Q

oxaloacetate is used to produce

A

glucose

148
Q

2 major fates of acetate & butyrate

A

1) generation of energy via TCA cycle
2) lipid synthesis

149
Q

2 mol of acetate = ( ) ATP

A

24

150
Q

what is the only gluconeogenic VFA

A

propionate

151
Q

why are circulating blood glucose levels lower in ruminants than monogastrics?

A

glucose is reserved exclusively for vita functions like in the brain so they absorb very little glucose from small intestine and rely on gluconeogenesis for the glucose they need

152
Q

bloat

A

viscous frothy foam in rumen that prevents eructation

153
Q

2 causes of rumen acidosis

A

VFA accumulation
lactic acid accumulation

154
Q

2 types of bloat

A
  • frothy
  • dry gas
155
Q

frothy bloat

A

bacteria produces slime in rumen that traps gases

156
Q

dry gas bloat

A

gas rises to space above digesta but animal is unable to release gas through eruptation

157
Q

2 causes of dry gas bloat

A
  • physical blockage of esophagus
  • damage to vagus nerve -> no signal to brain for rumen contractions to get rid of gases
158
Q

home remedy for bloat

A

vinegar

159
Q

trochar

A

used to release gas in cows who have bloat

160
Q

T or F: a trochar will not help with frothy bloat bc it needs an anti-foaming agent

A

T

161
Q

how to treat frothy bloat

A

stomach tube anti-foaming agent

162
Q

what is the digesta flowing into the stomach of monogastrics

A

amylopectin and dextrins

163
Q

T or F: no complete digestion of amylopectin without alpha dextrins present

A

T

164
Q

SARA

A

sub-acute ruminal acidosis

165
Q

SARA is more common in ( ) cattle than ( ) cattle

A

dairy, beef

166
Q

what is a major lactate producing bacteria in the rumen that may lead to SARA

A

strep. bovis

167
Q

lactic acid promotes growth of ( ) which will produce lots of lactic acid in rumen = acidosis

A

lactobacilli

168
Q

2 forms of lactic acid

A

1) L -> used by liver to produce glucose, can be metabolized
2) D: stays in bloodstream, cannot be metabolized

169
Q

3 symptoms of SARA

A

1) reduced or erratic feed intake
2) reduced rumination
3) lameness

ANSC 315 (9 decks)

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